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Step 1: Determine the Substep to Initiate Rezoning

 

 

 

 

 

 

 

Command

Description

Rezoning Comments

 

 

 

 

 

 

 

 

REMESH

Generates or

You can remesh more than one region at the same specified

 

 

obtains the new

substep during the rezoning process.

 

 

mesh required

 

 

 

 

 

for rezoning

After remeshing (REMESH,FINISH), the program gener-

 

 

 

ates contact elements (if any) and transfers loads and

 

 

 

boundary conditions automatically.

 

 

 

For more information, see Step 4: Perform the

 

 

 

Remeshing Operation (p. 99).

 

MAPSOLVE

Maps node and

After remeshing, this command maps the solved nodal and

 

 

element solu-

element solutions from the original (distorted) mesh to the

 

 

tions

new mesh and achieves equilibrium on the new mesh.

4.4. Step 1: Determine the Substep to Initiate Rezoning

Determining Why the Solution Terminated

To investigate the reason(s) why a solution terminated, you can enter the POST1 general postprocessor (/POST1) to review analysis results.

You can also use the GUI to select a substep for which restart files are available but results are not saved in a results file, generate the results for the selected substep, then review the results in POST1.

If the solution terminated because of a mesh distortion, it is a candidate for rezoning.

It is important to select a suitable substep at which to start rezoning. You must select a converged substep where the restart files are available.

The last converged substep is often a natural choice for initiating rezoning because there is typically

less of a remaining load to apply. However, the last converged substep may have more severely distorted elements which can cause larger errors when mapping solution variables (MAPSOLVE), in turn requiring more mapping substeps to balance residual forces or convergence failures. Rezoning from a substep with an extremely distorted mesh may also reduce the accuracy of the final solution, and can even cause the automatic transfer of boundary conditions after remeshing (REMESH,FINISH) to fail.

Typically, the best choice is the first, second, or third converged substep preceding the last converged substep. To determine the best possible substep to initiate rezoning, you may need to enter the POST1 general postprocessor (/POST1) to examine the deformed element shapes, and stress and strain distributions.

If no results data exists for a substep in the results file, you can use program restart features to generate results data for the substep, and then enter POST1 to examine the deformed shape; afterwards, you

can reenter the solution processor and initiate rezoning as usual.

Hints for selecting the best substep to initiate rezoning:

The substep should have an obvious mesh distortion but should contain no element having an internal angle too closely approaching, equal to, or exceeding 180 degrees.

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of ANSYS, Inc. and its subsidiaries and affiliates.

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The substep should have minimal penetration in contact. Try to avoid substeps where contact status has changed suddenly from previous substeps.

If an error occurs when the program transfers boundary conditions and loads after remeshing (REMESH,FINISH) and the old mesh is severely distorted, try the substep preceding the one most recently chosen.

The best substep is often not the last converged substep, but rather one of the several preceding the last one.

If the last few converged substeps are separated by very small time increments and you have already tried one or more of those substeps unsuccessfully, select a converged substep that is separated from the others by a larger time increment.

If you are still having difficulty obtaining a mesh of reasonable quality because the old mesh is too distorted, try the substep preceding the one most recently chosen.

If the mapping operation (MAPSOLVE) fails to converge even if you allow up to 500 substeps, try the substep preceding the one most recently chosen.

When you have determined the substep at which to initiate rezoning, proceed to Step 2. Initiate Rezoning (p. 98).

4.5. Step 2. Initiate Rezoning

Rezoning is based on an existing solution, so the initial solution must have terminated.

Because the simulation terminated, the rezoning process must begin with a clean database.

To start rezoning:

1.Clear the database (/CLEAR).

2.Reenter the solution processor (/SOLU).

3.Initiate rezoning, specifying the load step and substep at which rezoning should occur (REZONE,MANUAL,LDSTEP,SBSTEP).

Proceed to Step 3: Select a Region to Remesh (p. 98).

4.6. Step 3: Select a Region to Remesh

A region that you select (ESEL) for remeshing can contain the entire deformed domain or a portion of it. A selected region should consist of the same:

Material type

Element type (including the coordinate system and KEYOPT settings)

Thickness (real constant) for plane stress

Nodal coordinate system (except for boundary nodes which can have different nodal coordinate systems).

 

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98

of ANSYS, Inc. and its subsidiaries and affiliates.